<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .box {
            width: 400px;
            background: #333
        }
    </style>
</head>
<body>
    <div id="app">
        232
        <div class="box">

        </div>
        <button @click="toggle">toggle</button>
    </div>
</body>
<script src="https://cdn.bootcss.com/vue/2.6.8/vue.js"></script>
<script>
    var vm = new Vue({
        el: "#app",
        data: {
            title: '123'
        },
        beforeCreate: function() {

        },
        created: function() {

        },
        beforeMount: function() {

        },
        mounted: function() {
            console.log(3)
        }
    })
</script>
</html>